Hello,
I am not a programmer and I need some advise, please.
I thinking about using Raspberry Pi Zero W with a camera as a RFID/QR code reader with a small screen (3.5" - 8"). After reading a RFID code or capturing QR code and decoding it, I would like add some information and send it to a remote database.

If you are 'not a programmer' but want to use this project as a way into programming, I would use Python. Despite its quirks, it has a more gentle learning curve than most other common languages. If you don't plan to become at least something of a programmer, I am not sure how you plan to accomplish your project.

To many veriables to answer the OS question. Just about any OS would be well suited to your application.

The question of language, you will need to learn one at least. In the modern world everything takes on the structure of C, so that may be a good option. Though it is difficult to point to a true beginners tutorial on using C. The best one I know is the first 8 chapters of The C Programming Language, 2nd Ed, ANSI C, though that is a book that costs $20 (almost as much as a Raspberry Pi).

Give me a few minutes while I switch my RPi3B over to raspbian to give more pointers (need a JS web browser).

The Raspberry Pi is an ARM computer, that runs many Operating Systems, including Linux, RISC OS, BSD, Pi64, CP/M as well as many more.
Soon to add AROS to the list of operating systems.

And I would recommend staying away from the more difficult languages for now. That is stay away from the likes of Python, C++, Java, Algo, COBOL, etc. until you have a decent grasp on programming.

I used to recommend BBC BASIC to beginners, though things change and no one now days like even hearing the name of BASIC (despite BBC BASIC being more structured than many modern languages that do not even have typed variables [one of the complaints against other forms of BASIC that BBC BASIC solved])

The Raspberry Pi is an ARM computer, that runs many Operating Systems, including Linux, RISC OS, BSD, Pi64, CP/M as well as many more.
Soon to add AROS to the list of operating systems.

The question of language, you will need to learn one at least. In the modern world everything takes on the structure of C, so that may be a good option. Though it is difficult to point to a true beginners tutorial on using C. The best one I know is the first 8 chapters of The C Programming Language, 2nd Ed, ANSI C, though that is a book that costs $20 (almost as much as a Raspberry Pi).

I think that there is a reason why "it is difficult to point to a true beginners tutorial on using C". It is, at least in my opinion, a difficult first language for a beginner, and remains less than ideal for a 'casual user'. I have learnt and written substantial applications in many languages, from Apple II BASIC and 6502 Assembly Language through various other BASICS, C, Fortran, PDP-11 Assembler, 80n86 Assembler, and various special-purpose data manipulation languages. C was probably my favorite language when I was using it all the time, but, as a (now) only occasional programmer, I prefer languages that are either interpreted or have a programming environment that allows you easily to exercise bits of your code while you are developing it. I do most of my programming in VB.NET, using Visual Studio.

Python (which I have only started using fairly recently) is very good from this viewpoint, and also offers the ability to plug in modules which make many things that are difficult (particularly for a beginner) in other languages quite easy to accomplish. I think that the odds of a beginner making progress and not getting terminally frustrated are better with Python than with most other potential 'first languages'.

The question of language, you will need to learn one at least. In the modern world everything takes on the structure of C, so that may be a good option. Though it is difficult to point to a true beginners tutorial on using C. The best one I know is the first 8 chapters of The C Programming Language, 2nd Ed, ANSI C, though that is a book that costs $20 (almost as much as a Raspberry Pi).

I think that there is a reason why "it is difficult to point to a true beginners tutorial on using C". It is, at least in my opinion, a difficult first language for a beginner, and remains less than ideal for a 'casual user'. I have learnt and written substantial applications in many languages, from Apple II BASIC and 6502 Assembly Language through various other BASICS, C, Fortran, PDP-11 Assembler, 80n86 Assembler, and various special-purpose data manipulation languages. C was probably my favorite language when I was using it all the time, but, as a (now) only occasional programmer, I prefer languages that are either interpreted or have a programming environment that allows you easily to exercise bits of your code while you are developing it. I do most of my programming in VB.NET, using Visual Studio.

I would argue that C is about equal to BBC BASIC. I think the main trouble is the way it is taught, it is not taught for beginners instead it is assumed the person learning C is familiar with programming. The language is not the problem.

I will reserve my opinion about VB.NET. For BASIC I strongly prefer BBC BASIC V (aka ARM BASIC), which is a structured procedural language with typed variables, support for dereferencing indirected data, and the ability to directly call the OS on which it runs.

Python (which I have only started using fairly recently) is very good from this viewpoint, and also offers the ability to plug in modules which make many things that are difficult (particularly for a beginner) in other languages quite easy to accomplish. I think that the odds of a beginner making progress and not getting terminally frustrated are better with Python than with most other potential 'first languages'.

Python does not have properly typed variables. Remember this is one of the reasons that the 8-bit style BASIC's became frowned upon (most of which came from MicroSoft), that and the lack of parameterized procedures. Good habits from the start are better.

The Raspberry Pi is an ARM computer, that runs many Operating Systems, including Linux, RISC OS, BSD, Pi64, CP/M as well as many more.
Soon to add AROS to the list of operating systems.

Our opening poster, horizon2000, is not yet a programmer. A beginner to programming need a language that is quick an simple to get started with and all the hand holding they can get.

Python is such a language. Writing your first one line "Hello world" program is about as simple as it can get. From there it is simple steps to more complex things. There are tons of beginner friendly introductions to Python around the net and the documentation is excellent.

C is not a beginner friendly language. Not by a huge margin. Just the need to have a compile step is the first hurdle. Having to write a multi-line main function just to get "Hello world" output or do some simple arithmetic, with it's weird include statements, weird syntax, weird printf function etc is another big hurdle. And so on. When it comes to accessing a database from C it's a lot of hard work compared to Python and other modern high level languages.

C++ is way off the charts of complexity for a beginner. Unless one is using the Arduino where a lot of that is hidden from you and there is a simple IDE. That is not the case on the Pi.

Similarly, whilst any operating system will do for the stated application, a beginner needs hand holding. Going with Raspbian is the way to get lots of the best support available on the Pi.

Our opening poster, horizon2000, is not yet a programmer. A beginner to programming need a language that is quick an simple to get started with and all the hand holding they can get.

Python is such a language. Writing your first one line "Hello world" program is about as simple as it can get. From there it is simple steps to more complex things. There are tons of beginner friendly introductions to Python around the net and the documentation is excellent.

C is not a beginner friendly language. Not by a huge margin. Just the need to have a compile step is the first hurdle. Having to write a multi-line main function just to get "Hello world" output or do some simple arithmetic, with it's weird include statements, weird syntax, weird printf function etc is another big hurdle. And so on. When it comes to accessing a database from C it's a lot of hard work compared to Python and other modern high level languages.

Then go back to the good recommendation, BBC BASIC (in its modern form). It does not have the bad of Python and is a good beginner language, that does NOT have the bad of some other BASIC implementations.

C++ is way off the charts of complexity for a beginner. Unless one is using the Arduino where a lot of that is hidden from you and there is a simple IDE. That is not the case on the Pi.

C++ is the opposite of C. C is simple and eloquent, C++ is complex without reason.

Similarly, whilst any operating system will do for the stated application, a beginner needs hand holding. Going with Raspbian is the way to get lots of the best support available on the Pi.

The Raspberry Pi is an ARM computer, that runs many Operating Systems, including Linux, RISC OS, BSD, Pi64, CP/M as well as many more.
Soon to add AROS to the list of operating systems.

As for constructing and executing your remote database insert statement ODBC is probably where you should start looking, Afaik most database systems have ODBC

You may not need to learn any programing language beyond a few carefully constructed shell script commands,
invoke Zbar to scan and save its results in a known file and or location.
read the results construct an odbc insert statement and execute it
delete, move, rename or otherwise mark the scan results as dealt with.

as for rf tag reading the example code for the h/w you select should provide the basis for your data gathering so probably expand that to save its results so they can also be dealt with .